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6th International Conference on Accelerated Pavement Testing , NANTES, FRANCE, 27-/09/2021 - 29/09/2021; The concept of truck platooning is to take advantage of the connectivity technologies and automated driving support systems to link trucks in close formation (convoy) in order to increase transport efficiency, reduce fuel consumption and gas emissions while improving road safety. However, closely guided trucks following each other could have a different impact on road structures than the usual truck traffic. Notably, different studies with traffic simulators highlight the significant effect of the wander pattern of traffic on the damage observed on test road structures. On the other hand, the positioning systems could offer the opportunity to choose an optimized wander pattern of the trucks within the platoons, especially designed to mitigate the overall damage. In this context, the study reported in this paper addresses, through numerical simulations, the multi-loading effects of truck platoons on road structures for different configurations of wander patterns. The aggressiveness of these patterns is evaluated on the basis of the viscoelastic response of the pavement structures (strain field) computed using software ViscoRoute\textcopyright 2.0. Finally, recommendations on the choice of wander pattern configurations to be tested on APT facilities are proposed.

International audience; With the depletion of the virgin aggregates, many efforts have been oriented towards the recycling of the reclaimed asphalt pavement (RAP). However, quality control of the recycled product is required during the manufacture process. This research deals with the use of high-content RAP recycled asphalt mixture composed of 70% RAP based on experimental and micromechanical approaches. For the experimental part, a "Good" and a "Bad" blended mixture were manufactured in laboratory. Then, rheological measurements of the complex modulus of the different binders and mixtures were carried out. The micromechanical work is based on the generalised self-consistent scheme (GSCS) which was used to predict the mechanical properties of the recycled mixture. This approach aims to homogenize the heterogeneous material by taking into account both the intergranular porosity and the possible interactions between phases. The confrontation of the micromechanical model with the experimental results showed good agreements between measured data and predicted values of the complex modulus of the recycled asphalt. Moreover, it was highlighted from the experimental results that the blending process of the recycled mixture has a great influence on the viscoelastic properties of the recycled mixture. This result was also validated by the GSCS-based approach.

Recycling of old pavements is becoming a widespread technique; in order to preserve the natural resources of aggregates and binder, the materials reclaimed from the damaged layers of the pavements maintained are generally reincorporated in the material for new maintenance layers. However, recycling induces some technical challenges. In the case of the Hot mix asphalt (HMA), the most commonly used road construction material, one of the main concerns is ageing. Along with the heterogeneity of the RA properties in stockpiles, it is one of the main factors limiting the recycling rates in HMA. Therefore, the characterisation of ageing through reliable ageing indexes and of its impact on the bitumen physical properties is of paramount importance to improve the recycling techniques. The RILEM TC 237 SIB TG5 inherited a database from the previous work of the RILEM TC 206 ATB TG5 on a protocol for bituminous mixture ageing in laboratory. Taking advantage of these data, the work of the Task Group was first dedicated to a state of the art and an evaluation of the chemical ageing characterization through indexes based on Fourier Transform Infrared Spectroscopy (FTIR). In a second step, an attempt was made, in order to bring out the essential trends of the rheological data with ageing, by using a Huet modified rheological model. Then, exploring the potential of a recently developed method, an interpretation of these trends in terms of asphalt structure is suggested. Finally, possible empirical relationships between the chemical ageing indexes and the rheological parameters are investigated.

This work aims to develop asphalt mixes with 100% reclaimed asphalt pavements (RAP) as source of aggregates and bitumen emulsions stabilized by amine-functionalized lignin. To that end, reduced-temperature asphalt technologies between 80 and 130 °C were assessed. Previously, processing parameters of emulsions were evaluated by droplet size distribution and rheology measurements. Furthermore, a study combining Pendant drop and Sessile drop (on a prototype polyethylene surface) tests showed that emulsion aqueous phase containing modified lignin would be able to wet the hydrophobic surface of RAP. Manufactured asphalt mixes were characterized according to French design method for hot mixes, including gyratory compaction, rutting resistance, complex modulus and fatigue resistance tests. The results obtained showed that reduced-temperature asphalt mixes could be successfully prepared to meet French design requirements, which would further minimize impact to environment. However, mix design has required a semi-quantitative approach for estimating ‘active’ RAP binder content, by balancing the manufacturing temperature and the fresh bitumen required.

Within the framework of a sustainable development, manufacturing bituminous mixtures while reducing energy and using less new aggregates and new bitumen may be considered as an important topic, according to the quantities of asphalts mixtures produced for creating and maintaining road networks. This work aims to study the interest and the potential problems when coupling the warm mix asphalt technology (WMA) and the use of high ratio of reclaimed asphalt pavement (RAP) in the mixture. Initially, a study on managing RAP is performed, aiming to show that separating RAP aggregates in several fractions leads to a higher control of RAP in terms of homogeneity. Homogeneity of RAP is a key point for increasing recycling rates. The present study coupling WMA and RAP is based on the French design method for manufacturing asphalt concretes, which includes gyratory compaction tests, French wheel tracking tests, complex modulus tests and fatigue tests. However, the French design method does not take into account the physical and chemical aging of bituminous mixtures with time. As we consider that coupling WMA and RAP may lead to aging problems, it was decided to use an aging process before performing the standard tests. The results show that a WMA containing a high ratio of RAP has good performances according to the standard relative to this material, whatever the test. However, this material tends to be more sensitive to fatigue than hot and warm mixes without RAP.

Sustainable development policies currently in effect in civil engineering serve to promote techniques capable of saving both energy and raw materials; such techniques use a combination of warm mix asphalt (WMA) concretes with reclaimed asphalt pavement (RAP). One issue raised when combining WMA and RAP involves determining the potential lack of RAP binder remobilisation during blending with the new binder, i.e. the so-called double-coating phenomenon. This paper aims to present the results of an Attenuated Total Reflection (ATR) imaging by means of infrared microspectrometry on asphalt mixtures featuring high RAP content. In the context of a Ph.D. thesis program, this analysis is combined with a study of the mechanical performance of these materials (not presented herein). The main objective of this research work is to assess the blending and coating quality of the materials at the microscopic scale. The experimental program consists of evaluating raw aggregates, binders, RAP and asphalt mixtures by ATR-FTIR microspectrometry in order to generate pictures for analysis and interpretation according to two distinct methods, namely Principal Component Analysis (PCA) and Independent Component Analysis (ICA). This analysis protocol introduces markers inside asphalts, like SBS or EVA copolymers or carbonyl and sulfoxide indices. The first main result of this study is improved control over the ATR imaging tool and its enhanced potential for analysing bituminous mixtures. A protocol for preparing samples and interpreting their results can now be proposed; an actual asphalt concrete has been analysed, not merely a laboratory-produced sample, as indicated in the literature. As a second result, tracers have been set up to distinguish raw and RAP materials (aggregates and binders), thus representing an initial step to studying the double coating, although it would seem difficult to generalise this study to a wide array of mixtures. Lastly, let’s point out that ATR-FTIR imaging is a “localised” study, making the determination of bituminous material homogeneity at specimen or even stockpile scale a real challenge for the future.

Within the framework of the European Project SUP&R ITN a PhD the-sis is carried out to study the durability of the combination of high rates of re-claimed asphalt pavement and warm mix asphalt technologies. For this purpose the complex modulus and fatigue resistance of three different asphalt mixtures, in-cluding surfactant modified and foamed warm mix asphalts, combined with re-claimed asphalt pavement (RAP) has been studied. The extra value is given by the application of an ageing procedure based on the oxidation of compacted materials in laboratory. It follows the recommendations of the RILEM TC-ATB TG5, which distinguishes between short and long term ageing. Fourier Transform InfraRed (FTIR) tests were carried out on the extracted bitumens to quantify the oxidation levels. An increase of the norm and a decrease of the phase angle of |E*| at 15°C 10Hz with ageing and RAP addition are experienced for all the mixtures. Similar to what happens with the slopes of the fatigue laws that tend as well to increase. A consistent correlation is observed between these evolutions and the evolution of the carbonyl index calculated. This reflects a trend towards more brittle materials with predicted fatigue live improved for low strain levels but reduced for high strain levels. In general, the tendency is similar for all procedures, so the use of warm technologies combined with high RAP amounts may need to be considered.

Setting a method to evaluate the mechanical properties of an aged asphalt mix using a rapid chemical measurement from small samples, would be of high interest at different steps of a road structure life cycle: at the design step, to optimise the estimates of the service lifetime usually based on the properties of unaged materials; during the service life, to update the residual lifetime expectation of an existing structure according to the actual properties of the in situ aged materials; and at the end of the service life or for maintenance management, to evaluate the recyclability of the materials of the structure. This study was carried out aiming at comparing results from Fourier Transform InfraRed and Dynamic Shear Rheometer tests. Experimental data came from an international round robin test, organised by the RILEM TC ATB, designed to set an ageing protocol on loose bituminous mixtures. The evolutions of the carbonyl index (ICO) calculated from the FTIR spectra are compared to the evolutions of the parameters of a modified Huet Rheological Model (1S2P1D) fitted on the experimental linear viscoelastic data measured on the recovered binder. A significant relationship is observed suggesting that chemical and rheological properties could be correlated. Based on this observation, a method is proposed for predicting the G* values of a binder aged at a given ΔICO level. Subsequently, this method could be used to predict the complex modulus E* of a given mix from the shear modulus G* of the binder using existing binder/mix transfer models.

In recent years, as a result of both envi-ronmental policy and industrial economic strategy, the amount of asphalt pavement that has been recycled has risen dramatically. As a result of this, several inter- national research projects have shown the need for improvements in reclaimed asphalt (RA) character- isation to support these higher recycling rates. During the life of a pavement, as well as the structural damage induced by traffic, the intrinsic properties of asphaltic materials are affected through the oxidative ageing of the bituminous binder. The molecular changes asso- ciated with this oxidation can be monitored via variations in Fourier transform infrared (FTIR) spec- tra. Therefore, if the relationships between binder properties, such as penetration, softening point and complex shear modulus and the spectra parameters can be established, the characterisation of RA pro- duced by the milling of old pavements can be greatly improved. However, the interpretation of oxidation parameters from these spectra is not straightforward, and many different techniques are used to calculate them in the asphalt community. This paper gives a brief overview of asphalt oxidation and the FTIR principle. It then presents the results from four different calculation methods for the oxidation param- eters applied to a set of more than 100 spectra obtained during the RILEM TC-ATB-TG5 round robin test. From this study, it is obvious that the conclusions of the analysis performed on the same set of raw spectra can differ considerably according to the FTIR oxida- tion index calculation method adopted. Using the RILEM database, the potential links between a given ageing index and the physical properties are then evaluated. As a result of this study it can be concluded that ageing comparison through FTIR should be considered as relative and restricted for use in measurements at different ageing steps on the same type of initial mixture. For FTIR spectra to be comparable between different laboratories, harmoni- sation of the data acquisition procedures is needed. Also the different calculation methods of the oxidation indicators seem to reflect different physical properties. So a first step toward harmonisation would be to agree on the relevant physical properties actually needed for efficient RA characterisation. This could then lead to a common FTIR index calculation method, which would reflect the properties of interest. For this, additional research is needed to improve knowledge of the relationship between the chemical oxidative process of a binder and the evolution of its physical properties

This chapter focuses on permanent deformation, which is at the origin of pavement rutting. First experimental laboratory tools and associated analyses related to permanent deformations are presented. It is either material tests, that can be homogeneous or giving a simple empirical characteristic, or non-homogeneous Structural/Specimen tests.

This chapter first presents the results of a survey perfomed on the practices used in Europe. This survey is first report on the subject and could be usefully completed by the states of the art prepared in the framework of the Re-road and Direct-Mat European projecys.

In the framework of the RILEM TC 206-ATB TG3, a Round Robin Test (RRT) has been performed in order to evaluate the reproducibility of the French Wheel Tracking Test (FWTT) on a mix made with Polymer Modified Bitumen (PmB). For this mixture, some particular problems had been reported, such as heating of the sample due to friction and sticking of the binder to the wheel. Two procedures, called anti-overheating and anti-sticking procedures, have been proposed by the group in order to improve the reproducibility of the wheel tracking tests. These procedures are assessed. Causes of scattering are discussed. Differences between the tyres used during this RRT as a possible origin of scattering are discussed, as well as temperature peaks and over-compaction of specimens.

The paper presented first results elaborated during the European Research Project Re-road which aims at the development of techniques for increasing the recycling rates of reclaimed asphalt. During service life surface asphalt courses are subjected to aging due to oxidation effects which causes the hardening of the binder and thereby a change in the chemical, physical and mechanical properties of the material. Surface courses often contain highly modified binders as well as special additives for improving the performance characteristics. As these layers inhibit the shortest service lives compared to other road construction layers every year high amounts of reclaimed surface asphalt are available for recycling. The question is raised how the reclaimed asphalt consisting of high quality and costly material components can be recycled for optimal added value. To analyze the asphalt mix service life performance and its recyclability during mix design a laboratory method was developed to simulate the real in-situ aging. First the effects of site aging on the binder and asphalt characteristics were presented. Three laboratory aging methods were discussed which aimed the accelerated aging which meets similar property changes as site aging. At last the effects of two different laboratory aging methods on the same SMA mixture were compared.